CM871 and CM876 Electronic Control Systems, ISX and ISM Engines – FAULT CODE 1972

Exhaust Gas Temperature 3 – Data Valid but Above Normal Operational Range – Moderately Severe Level


Overview

CODE REASON EFFECT
Fault Code: 1972
PID: S328
SPN: 3245
FMI: 0/16
LAMP: Amber
SRT: 

Exhaust Gas Temperature 3 – Data Valid but Above Normal Operational Range – Moderately Severe Level. The aftertreatment diesel particulate filter outlet temperature sensor reading has exceeded the maximum temperature limit.

Active aftertreatment diesel particulate filter regeneration will be disabled.

ISX and ISM – Aftertreatment Temperature Sensors
SMALL | MEDIUM | LARGE

Circuit Description

The aftertreatment temperature sensors are used by the electronic control module (ECM) to monitor the engine exhaust temperatures in the aftertreatment system. The aftertreatment temperature sensors are thermistors and change resistance based on the temperature being measured. The ECM provides a 5 volt reference voltage to the sensor. The ECM monitors the change in signal voltage and converts this to a temperature value.

When the exhaust gas temperature is low, the thermistor resistance is high. The ECM signal voltage only pulls down a small amount through the sensor to ground. Therefore, the ECM senses a high signal voltage (low temperature). When the exhaust gas temperature is high, the thermistor resistance is low. The signal voltage pulls down a large amount. Therefore, the ECM senses a low signal voltage (high temperature).

Component Location

The aftertreatment diesel particulate filter outlet temperature sensor is located in the aftertreatment system. It is located at the outlet of the aftertreatment diesel particulate filter. Refer to the original equipment manufacturer (OEM) service manual.

Conditions for Running the Diagnostics

This diagnostic runs continuously when the keyswitch is in the ON position and when the engine is running.

Conditions for Setting the Fault Codes

The aftertreatment diesel particulate filter outlet temperature sensor reading exceeds 675°C [1247°F] for 5 seconds and then returns below 575°C [1067°F]. This needs to occur five times before the fault code is logged.

Action Taken When the Fault Code is Active

  • The ECM illuminates the amber CHECK ENGINE light immediately when the diagnostic runs and fails.
  • Active aftertreatment diesel particulate filter regeneration will be disabled.
  • Exhaust gas recirculation (EGR) valve operation will be disabled.

Conditions for Clearing the Fault Code

The ECM will turn off the amber CHECK ENGINE light and the fault code will be set to inactive when the keyswitch is cycled.

Shop Talk

Verify the electronic control module (ECM) calibration is correct. Check the calibration revision history found on QuickServe™ Online for applicable fixes to the calibration stored in the ECM. If necessary, calibrate the ECM. Refer to Procedure 019-032 in Section 19.

An intermittent fault code condition may be caused by the aftertreatment sensor and related wiring being shorted or damaged (melted), due to component interference. If an intermittent fault code condition exists, inspection of the aftertreatment sensors and wiring for any possible damage is required. Use the appropriate securing methods to make sure the sensor and wiring are not interfering or contacting other components.

Possible causes of this fault code include:

  • A damaged fuel injector causing unburned fuel to enter the exhaust system
  • A damaged aftertreatment fuel injector
  • Aftertreatment diesel particulate filter outlet temperature sensor failed in-range
  • A face plugged diesel oxidation catalyst
  • Excessive engine oil being introduced into the exhaust system from the engine or turbocharger
  • Aftertreatment temperature sensor has shorted and/or the sensor wiring or connector has been damaged.

Refer to Troubleshooting Fault Code t05-1972

Last Modified:  09-Jul-2010